Photographic camera having a piezo-electric actuating element

ABSTRACT

A photographic camera of the type including a piezo-electric actuating element driven by energy accumulated in a capacitor for actuating a shutter wherein the piezo-electric element operates in stability to assure accurate appropriate opening and closing operation of the shutter of the camera and the capacitor is charged up rapidly to allow subsequent photographing operation to be done in a minute. In the camera, a charged voltage of the capacitor is checked several times to determine if it is sufficient to assure proper operation of the piezo-electric element, and if a then required level is not reached, then the capacitor is charged to the required voltage. While the capacitor is being charged, charging of a capacitor for a flash is inhibited. For operation of the shutter, a negative voltage is first applied across the piezo-electric element to set the same to its fixed home position, and then a positive voltage is applied to move the shutter from the home position to a predetermined opening position, whereafter the negative voltage is applied again to return the shutter to its initial position rapidly. The position of the shutter is also checked to assure proper operation of the camera.

This application is a divisional, of application Ser. No. 013,561, filedFeb. 11, 1987 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a photographic camera, and more particularlyto a camera having a piezo-electric actuating element which is distortedin response to a voltage applied thereto.

2. Description of the Prior Art

Conventionally, various proposals have been made to a camera of the typewherein a piezo-electric actuating element as described above which isalso known as a bimorph is employed for actuation of a photographinglens for focusing or of a shutter. Typical ones of such cameras aredisclosed, for example, in Japanese Patent laid-open No. 60-144726 andin Japanese Patent Laid-open No. 59-204014.

In order to apply a stabilized high voltage across such a piezo-electricactuating element as is used for actuation of a lens or a shutter todrive the piezoelectric actuating element in stability, it may beadvisable to once accumulate in a capacitor a charge of a voltagenecessary to drive the piezo-electric actuating element in stability andthen supply the charge thus accumulated to the piezo-electric actuatingelement upon actuation of the same for photographing. Further, as it isconsidered that subsequent photographing may be done in a moment, it isnecessary that, when a subsequent photographing operation is started,the capacitor is already charged up to a voltage sufficient to drive thepiezoelectric actuating element in stability because actuation of ashutter or a lens by the piezo-electric actuating element is essentiallyrequired for such photographing.

In other words, if a subsequent photographing operation is startedbefore the capacitor is charged up to a voltage sufficient to drive thepiezo-electric actuating element in stability, the lens or shutter whichis connected to be actuated by the piezo-electric actuating element willnot operate regularly. Accordingly, there is the possibility thatphotographing in error such as photographing with out of focus conditionor with improper exposure may be done.

Meanwhile, a main capacitor of a flash device which is provided tosupply energy for emission of light to a xenon tube of a flash for flashphotographing makes a high load to a power source. Accordingly, if thecapacitor for the piezo-electric actuating element is charged insimultaneous relationship with the main capacitor of a flash device,much time is required to completely charge up both the capacitors, whichwill disable subsequent photographing to be performed in a moment.Accordingly, such simultaneous charging of both the capacitors is notpreferable.

Further, such a piezo-electric actuating element presents a followingproblem due to its hysteresis characteristic which is well known in theart. In particular, if it is assumed, for example, that a voltage of 0volts is applied across a piezo-electric actuating element at an initialposition and that a voltage of 200 volts is first applied across thepiezo-electric actuating element in order to actuate a shutter and thenthe voltage of 0 volts is applied again across the piezo-electricactuating element after operation of the shutter, the piezo-electricactuating element will not return to its initial position due to itshysteresis characteristic. Accordingly, if the voltage application tothe piezoelectric actuating element is controlled upon subsequentoperation of the shutter on the assumption that the piezo-electricactuating element has been returned to its initial position, operationin error will occur.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to provide a camerawhich can resolve the drawbacks described above that are derived fromuse of a piezo-electric actuating element for actuation of a lens or ashutter of the camera.

It is another object of the invention to provide a camera of the typeincluding a piezo-electric actuating element which is driven by a chargeaccumulated in a capacitor to control a lens or a shutter of the camera,wherein the specific disadvantage described above that is derived from aphotographing operation started when the capacitor for actuation of thepiezo-electric actuating element is not yet charged up sufficiently.

It is a further object of the invention to provide a camera of the typeincluding a capacitor for driving a piezo-electric actuating element anda main capacitor for driving a flash for flash photographing, wherein adefect that simultaneous charging of the capacitors will increase thetime required to charge up the capacitors can be eliminated.

It is a yet another object of the invention to provide a camera of thetype including a capacitor for driving a piezo-electric actuatingelement and a main capacitor for driving a flash for flashphotographing, wherein the capacitor for driving the piezo-electricactuating element can be charged up rapidly to allow the camera toeffect subsequent photographing in a moment.

It is a still further object of the invention to provide a camerawherein, before a photographing operation is started, a capacitor whichis charged to supply energy to a piezo-electric actuating element thatis used to actuate a shutter or a lens of the camera is charged withoutfail to a voltage sufficient to drive the piezoelectric actuatingelement in stability.

It is a still further object of the invention to provide a camerawherein opening and closing operation of a shutter can be controlledefficiently using a piezoelectric actuating element.

It is an additional object of the invention to provide a camera of thetype including a shutter which serves also as an aperture diaphragm,wherein a program chart indicating a relationship between a shutterspeed and an aperture value with respect to brightness of an object canbe changed by changing the opening speed of the shutter.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operator, togetherwith further objects and advantages thereof, may best be understood byreference to the following description, taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an electric circuit of a cameraaccording to a preferred embodiment of the present invention;

FIG. 2 is a front elevational view showing an exposure controllingmechanism of the camera of FIG. 1;

FIGS. 3a and 3b are a front elevational view and a top plan view,respectively, showing, in an enlarged scale, part of the exposurecontrolling mechanism of FIG. 2;

FIGS. 4a and 4b front and side elevational views, respectively, showinga lens actuating mechanism of the camera of FIG. 1;

FIG. 5 is a front elevational view showing another lens actuatingmechanism in a modified form;

FIG. 6 is a similar view but showing a further lens actuating mechanismin another modified form;

FIG. 7a is a graph illustrating a characteristic of a piezo-electricactuating element and FIG. 7b is an enlarged schematic view showingconstruction of such a piezo-electric actuating element;

FIG. 8 is a circuit diagram showing detailed construction of an exposurecontrolling circuit and a switching circuit of the circuit of FIG. 1;

FIG. 9 is a circuit diagram showing detailed construction of a lensactuating circuit of the circuit of FIG. 1;

FIG. 10 is a circuit diagram showing construction of a flash circuit ofthe embodiment shown in FIG. 1;

FIG. 11 is a program chart illustrating typical exposure programsemployed in the camera of FIG. 1;

FIGS. 12a, 12b and 12c are flow charts of an interrupt routineillustrating a flow of operations of the camera of FIG. 1;

FIGS. 13a, 13b and 13c are flow charts of different subroutines eachillustrating operation of the camera of FIG. 1 when one of differentexposure programs is selected;

FIG 14 is a flow chart illustrating a subroutine of "LENS ACTUATION" ofthe flow chart of FIG. 12c;

FIG. 15 is a flow chart illustrating a subroutine of "AE" of the flowchart of FIG. 12c;

FIG. 16 is a circuit diagram showing a lens actuating circuit in amodified form;

FIG. 17 is a flow chart illustrating peculiar operation of a camerawhich incorporates the lens actuating circuit of FIG. 16;

FIG. 18 is a flow chart illustrating a subroutine of "LENS ACTUATION" ofFIG. 17;

FIG. 19 is a circuit diagram showing an entire electric circuit of acamera according to another embodiment of the invention;

FIGS. 20a, 20b and 20c are flow charts of an interrupt routineillustrating a flow of operations of the camera of FIG. 19;

FIG. 21 is a flow chart illustrating a subroutine of "P.E.E. BOOSTING"of the flow chart of FIG. 20c;

FIG. 22 is a circuit diagram showing an exposure controlling circuit ina modified form;

FIGS. 23a, 23b, and 23c are flow charts of an interrupt routineillustrating a flow of operations of a camera which incorporates theexposure controlling circuit of FIG. 22 ;

FIG. 24 is a flow chart illustrating a subroutine of "P.E.E. RESETTING"of the flow chart of FIG. 23b;

FIG. 25 is a flow chart illustrating a subroutine of "AE" of the flowchart of FIG. 23c;

FIG. 26 is a flow chart of part of an interrupt routine illustratingpeculiar operation of a camera which incorporates the lens actuatingmechanism of FIG. 6;

FIG. 27 is a flow chart illustrating a subroutine of "LENS ACTUATION" ofthe flow chart of FIG. 26;

FIG. 28 is a flow chart illustrating a modified subroutine of "P.E.E.RESETTING" of the camera which incorporates the exposure controllingcircuit of FIG. 22;

FIG. 29 is a front elevational view showing a mechanism for actuating ashutter of a camera according to a further embodiment of the invention;

FIG. 30 is a cross sectional view taken along line XXX--XXX of FIG. 29;

FIG. 31 is a fragmentary perspective view showing the mechanism of FIG.29;

FIG. 32 is a block diagram showing an electric circuit of the camera ofFIG. 29;

FIGS. 33a, 33b and 33c are flow charts of a routine illustrating a flowof operations of the camera of FIG. 29;

FIG. 34 is a circuit diagram showing detailed construct of apiezo-electric element driving circuit of the circuit of FIG. 32;

FIG. 35 is a graph illustrating characteristics of opening of a shutterrelative to a time of application of a voltage to a piezo-electricelement of FIG. 34; and

FIG. 36 is a flow chart of a modified routine corresponding to FIG. 33a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described indetail with reference to the drawings.

Referring first to FIG. 1, there is illustrated an electric circuitwhich is used in a camera of a preferred embodiment of the presentinvention. The circuit shown includes a microcomputer 1 which performssequencing control of the camera and calculations, a photometry circuit2 which sends a brightness value Bv corresponding to a brightness of anobject as a digital signal to the microcomputer 1, a film sensitivityreading circuit 3 which sends a read film sensitivity value Sv as adigital signal to the microcomputer 1, a film winding circuit 4including a motor for taking up a film, and a boosting circuit 5 forboosting a low voltage of a power source battery MB to high voltages.The circuit of FIG. 1 further includes switching circuits 6, 7, 8 forselectively supplying the high voltages to an exposure controllingcircuit 9 for controlling the exposure of the camera in response to anexposure signal from the microcomputer 1, a lens actuating circuit 10for actuating a lens in response to a lens actuating signal from themicrocomputer 1, and a flash controlling circuit 11 for causing emissionof flash light in response to a light emitting signal from themicrocomputer 1, respectively.

The circuit of FIG. 1 further includes a finder display circuit 12 forproviding indications of warning of a low brightness and permission ofphotographing within a field of view of a finder, and a distancemeasuring circuit 13 for measuring a distance from the camera to anobject and for sending the thus measured distance as a digital signal tothe microcomputer 1.

In addition to the main power source MB for supplying electric power tothe entire circuitry of the camera mentioned above, the circuit of FIG.1 further includes a backup power source BB for supply electric poweronly to the microcomputer 1. The circuit further includes diodes D₁, D₂for preventing reverse charging, and a power supply transistor Tr₁ whichis controlled by an output terminal OP₀ of the microcomputer 1.

The circuit of FIG. 1 further includes various switches including a lenscover actuated switch S₀ which is turned on when a lens cover not shownis opened. The microcomputer 1 executes a routine named "S₀ ON"described hereinbelow in response to a change of an input to aninterrupt terminal INT₁ thereof from an H level to an L level due toturning on of the switch S₀.

A photometry switch S₁ is turned on in response to depression of ashutter release button not shown to a first stroke. The microcomputer 1executes an interrupt routine named "S₁ " described hereinbelow inresponse to a change of the switch S₁ from off to on or from on to off.A one shot pulse generating circuit 14 is connected to the photometryswitch S₁ and generates a single pulse in response to a change of thephotometry switch S₁ from on to off or from off to on. A release switchS₂ is turned on in response to depression of the shutter release buttonto a second stroke which is greater than the first stroke, and exposureoperation is initiated by the turning on of the switch S₂ Further, a oneframe switch S₃ is turned on upon completion of winding up of a film byone frame distance, and an opening monitor switch S₄ composed of aphotocoupler is turned on just before a shutter is actuated in anopening direction to start exposure. The output of the photocouplernormally presents a voltage of a high level (hereinafter referred to as"H" level), but when the shutter comes to its initial position, anelectric current flows through a light receiving portion thereof so thatit will output a voltage of a low level (hereinafter referred to as "L"level). In particular, the switch S₄ is provided to compensate fordeviations of the initial position of the shutter. Accordingly, where ashutter which presents no fluctuations in its initial position isemployed, the switch S₄ is not necessitated. A switch S₅ is turned onwhen the shutter is returned to its initial position after it has beenclosed.

The circuit of FIG. 1 further includes a pair of mode switches S₆ and S₇for setting an exposure mode therethrough. The camera of the presentembodiment has three exposure modes including an aperture priority mode,a shutter speed priority mode and a normal mode, and one of the threemodes is selectively determined by a combination of on and off states ofthe switches S₆ and S₇.

Now, a shutter actuating mechanism for a shutter served also as anaperture in the present embodiment and a method of actuating the shutteras well as a mechanism for and a method of actuating the lens will bedescribed briefly. The shutter and lens in the present embodiment areactuated indirectly by piezo-electric actuating elements providedindividually therefor.

At first, a mechanism for actuating a shutter will be described withreference to FIG. 2. The mechanism shown includes a pair of shutterleaves or blades 15, 16 each having a small hole 15a, 16a and a slot15c, l6c formed therein, respectively, and supported for pivotal motionon a common shaft 17. A pin 18 is implanted on an arm 15b extending fromthe shutter leaf or blade 15. An opening and closing lever 19 having twoarms 19a and 19b is supported on a shaft 20. A pin 19c is implanted atan end portion of the arm 19a of the lever 19 and engaged in slots 15c,16c formed in the shutter blades 15, 16. A piezo-electric actuatingelement Bi₁ is connected at a free end thereof to the arm 19b of thelever 19 by means of a pin 21. Here, the distance from the shaft 20 tothe pin 19c is about 5 times of the distance from the shaft 20 to thepin 21. Accordingly, a motion f the piezoelectric actuating element Bi₁is transmitted in an amplified magnitude to the shutter blades 15, 16.

The piezo-electric actuating element Bi₁ is supported in the form of acantilever with a left end portion thereof fixed in FIG. 2 and isconnected at the free right end thereof to the lever 19 as seen in theenlarged views of FIGS. 3a and 3b. Referring to FIGS. 3a and 3b, thepiezo-electric actuating element Bi₁ includes a metal substrate 22 and apair of piezo-electric elements 23, 24 located on opposite faces of themetal substrate 22. An end of the substrate 22 is extended so as to forma bent lug 22a in which the pin 21 is engaged.

With the construction described above, if electrodes of thepiezo-electric actuating element Bi₁ are shorted, it will pivot theshutter blades 15, 16 to their respective closed positions via theopening and closing lever 19 as seen in FIG. 2. To the if contrary, if avoltage is applied between the electrodes, the piezo-electric actuatingelement Bi₁ will be deformed to pivot the opening and closing lever 19to open the shutter blades 15, 16.

A lens actuating mechanism employed in the camera of the embodiment isshown in FIGS. 4a and 4b. The lens actuating mechanism shown includes aphotographing lens L which is held integrally on a holding frame 25. Theholding frame 25 has a support arm 25a fitted on a guide bar 27implanted on a base plate 26. The holding frame 25 further has a pair ofarms 25b, 25c individually formed in a spaced relationship by an angleof 120 degrees from the support arm 25a thereon. Thus, the holding frame25 is supported for movement in a direction of an optical axis of thelens by means of the guide bar 27 and is urged in a leftward directionin FIG. 4b, that is, in a retracting direction, by a spring 28 toresiliently engage the arms 25a, 25b, 25c of the holding frame 25 withthree cam sections 29a of a focusing cam ring 29.

The cam sections 29a of the focusing cam ring 29 have an identical shapeand are located in a spaced relationship by an angle of 120 degrees fromeach other. The focusing cam ring 29 further has ratchet teeth 29bformed over an entire periphery thereof, and three projections 29clocated in a spaced relationship by an angle of 120 degrees from eachother. The focusing cam ring 29 is supported for rotation around theoptical axis but is allowed to rotate only in a clockwise direction inFIG. 4a while rotation thereof in the opposite counterclockwisedirection is prevented by a spring plate 30 which engages with a ratchettooth 29b of the cam ring 29.

A feed pawl lever 31 has a feed pawl 31a for engagement with a ratchettooth 29b of the cam ring 29 and is pivotally connected to an end ofanother piezo-electric actuating element Bi₂ and urged in acounterclockwise direction in FIG. 4a to resiliently engage the feedpawl thereof with a ratchet tooth 29b of the cam ring 29. Thepiezo-electric actuating element Bi₂ is supported in the form of acantilever with a lower end portion thereof fixed in FIG. 4a, and theopposite free end portion thereof is connected to the feed pawl lever 31as described hereinabove.

In an initial condition shown in FIG. 4a, the arms 25a, 25b and 25c ofthe holding frame 25 contact with lower portions of the cam sections 29aof the cam ring 29, and accordingly the photographing lens L is in aretracted position together with the holding frame 29. Meanwhile, one ofthe projections 29c of the cam ring 29 engages with the pin 18 extendingthrough and from an elongated hole 26a in the base plate 26 to hold theshutter blades 15, 16 to the respective closed positions.

With the construction described above, if a voltage is applied betweenelectrodes of the piezo-electric actuating element Bi₂ and then theelectrodes are shorted, the piezo-electric actuating element Bi₂ will befirst bent in a counterclockwise direction in FIG. 4a with respect tothe lower fixed end thereof and then will return substantially to itsinitial shape. Upon this single vibration, the feed pawl 31a of the feedpawl lever 31 is first moved in a leftward direction in FIG. 4a over aratchet tooth 29b and then draws the ratchet tooth 29b in the oppositerightward direction in FIG. 4a to rotate the cam ring 29 one tooth spacein the clockwise direction. As such vibration is repeated, the ratchetteeth 29b are fed one after another in the clockwise direction so thatthe photographing lens L is advanced a distance corresponding to thenumber of the ratchet teeth 29b thus fed together with the lens holdingframe 25. It is to be noted that each of the cam sections 29a is formedin such a manner as to increase the height while gradually moderatingthe slope from the bottom thereof. Accordingly, even though the urgingforce of the spring 28 increases as the lens holding frame 25 advances,a force required to feed the cam ring 29 one tooth space does notincrease very much.

It is to be noted here that a lever for amplifying the vibration of thepiezo-electric actuating element Bi₂ similar to the lever 19 shown inFIG. 2 may additionally be provided between the piezo-electric actuatingelement Bi₂ and the feed pawl 31a.

FIG. 5 shows a modified form of the lens actuating mechanism shown inFIG. 4a. The modified lens actuating mechanism includes a spring 32 forurging the cam ring 29 to its initial position, and a stopping lever 33urged to a position in which it engages with a ratchet tooth 29b of thecam ring 29 to prevent the cam ring 29 from returning to its initialposition.

The piezo-electric actuating element Bi₂ is controlled to make smallvibration of a small magnitude and large vibration of a large magnitudein a counterclockwise direction in FIG. 5. If a small vibration occurs,then the feed pawl lever 31 will feed the ratchet teeth 29b one toothdistance. To the contrary, if a large vibration occurs, then thestopping lever 33 will be pushed against the urging thereof by an end ofthe feed pawl lever 31 and thus moved to a position in which it is clearof the ratchet teeth 29b. Consequently, the cam ring 29 is returned toits initial position by the urging force of the spring 32.

Referring now to FIG. 6, another modified lens actuating mechanism isshown. The modified lens actuating mechanism shown includes a switch 34for detecting that the cam ring 29 is rotated to its initial position.

Here, the piezo-electric actuating elements Bi₁, Bi₂ both have avoltage - displacement characteristic as shown in FIG. 7a, and if avoltage is applied across the piezoelectric actuating element with oneend thereof fixed, the other end thereof will be displaced. Now, if apositive voltage is applied to one piezo-electric element A shown inFIG. 7b relative to the other piezo-electric element B, thepiezo-electric actuating element Bi₁ will be bent in a directionindicated by an arrow mark in FIG. 2. This motion will move the openingand closing lever 19 located contiguously to the opposite end remotefrom the fixed end of the piezo-electric actuating element Bi₁ to openthe shutter. The degree of exposure is determined by the amount of thismotion.

As a method of controlling the amount of the displacement or motion ofthe piezo-electric actuating element, following two methods may beexpected: (a) to control an applied voltage to control the amount of thedisplacement; and (b) to monitor the amount of the displacement and stopapplication of a voltage if a predetermined amount of displacement isreached. However, in the case of the method (b), the cost becomes highbecause means for monitoring the amount of displacement (for example, anencoder) is required. Therefore, the method (a) is employed in thepresent embodiment. In the present embodiment, as the method (a), avoltage is controlled by accumulating charge in a capacitor component ofthe piezo-electric actuating element itself and by monitoring a timerequired for such accumulation.

Referring now to FIG. 8, part of the circuit of FIG. 1 including acircuit for controlling the shutter is shown in more detail. The circuitshown includes the boosting circuit 5, the switching circuits 6, 7, 8including transistors Tr₆ to Tr₁₀, and the exposure controlling circuit9.

The boosting circuit 5 includes transistors Tr₂ to Tr₅, a resistor R₁and a DC-DC converter DC-DC. Two different boosted voltages are takenout from a secondary winding of the DC-DC converter DC-DC. Of the twoboosted voltages, a voltage V₅ which is taken out via a diode D₅ and thetransistor Tr₁₀ is supplied to the flash circuit 11 shown in FIG. 10while the other voltage V₃ which is taken out via another diode D₃ andthe transistor Tr₇ (here, V₃ <V₅) is supplied to the exposurecontrolling circuit 9. Further, the other voltage V₄ which is taken outvia a further diode D₄ and the transistor Tr₈ (here, V₄ =V₃) is suppliedto the lens actuating circuit 10 shown in FIG. 9.

Of the circuits, the exposure controlling circuit 9 shown in FIG. 8includes a capacitor C₂ for accumulating charge therein, a voltagedetecting circuit BC₁ for detecting a voltage accumulated in thecapacitor C₂, a piezo-electric actuating element Bi₁, another capacitorC₃ connected in parallel to the piezo-electric actuating element Bi₁,and transistors Tr₁₁ to Tr₂₀

The voltage detecting circuit BC₁ produces, when a voltage of 200 voltsis detected, a detection signal of an "H" level to an input terminal IP₈of the microcomputer 1. When such a detection signal is received, themicrocomputer 1 turns off the transistors Tr₆, Tr₇, Tr₈ of the switchingcircuits 6, 7, 8, and further turns off the boosting controllingtransistor Tr₂ of the boosting circuit 5 to stop boosting of theboosting circuit 5.

Now, the controlling transistors Tr₁₁ to Tr₂₀ which apply the voltageobtained in this manner across the piezo-electric actuating element Bi₁will be described. The shutter of the present embodiment is designed tohave combination of the three different shutter speeds (T) and threedifferent aperture values (f-number) with respect to a change inbrightness of an object as shown in FIG. 11. In order to realize suchcombinations, the current flow through the piezo-electric actuatingelement Bi₁ is controlled to control charging of the capacitor componentof the piezo-electric actuating element Bi₁ to determine a slope of anexposure program line shown in FIG. 11 (a combination of an aperturevalue and a shutter speed). The amount of exposure is controlled bycontrolling the shutter speed (exposure time).

Here, the current flow through the piezo-electric actuating element Bi₁is controlled by a combination of the transistors Tr₁₁, Tr₁₂ and aresistor Ra, another combination of the transistors Tr₁₃, Tr₁₄ and aresistor Rb, and a further combination of the transistors Tr₁₅, Tr₁₆ anda resistor Rc. Then, if Ra<Rb<Rc where Ra, Rb, Rc represent resistancesof the resistors Ra, Rb, Rc respectively, then when the transistors Tr₁₁and Tr₁₂ are turned on, the amount of exposure is controlled inaccordance with the program line (a) shown in FIG. 11, and when thetransistors Tr₁₃ and Tr₁₄ are turned on, the amount of exposure iscontrolled in accordance with the program line (b) shown in FIG. 11, butwhen the transistors Tr₁₅ and Tr₁₆ are turned on, the amount of exposureis controlled in accordance with the program line (c) shown in FIG. 11.This will be hereinafter described.

The side of the piezo-electric actuating element Bi₁ connected to thecollector of the transistor Tr₁₈ corresponds to the piezo-electricelement B of FIG. 7b. Now, if the transistors Tr₁₁, Tr₁₂ and thetransistor Tr₁₈ are turned on, the piezo-electric element B shown inFIG. 7a is grounded while a voltage of 200 volts is applied to thepiezo-electric element A via the resistor Ra and the transistor Tr₁₂.Consequently, charge is accumulated in the capacitor component CB₁ ofthe piezo-electric actuating element Bi₁ and the capacitor C₃ connectedin parallel to the piezo-electric actuating element Bi₁ to raise thecharged voltage of them. Accordingly, the piezo-electric actuatingelement Bi₁ is bent as time passes, and in this case the opening of theshutter presents a waveform as shown by the program line (a) in FIG. 11.Here, the capacitor C₃ is provided to control the magnitude ofdisplacement of the piezo-electric actuating element Bi₁ relative to thetime which displacement appears because the capacitance of the capacitorcomponent CB₁ of the piezo-electric actuating element Bi₁ is small.

Then, as a time t₁ shown in FIG. 11 is reached, the applied voltageacross the piezo-electric actuating element Bi₁ reaches 200 volts, andthereafter the piezoelectric actuating element Bi₁ is left in thiscondition. Here, if a predetermined amount of exposure is reached beforethe applied voltage across the piezo-electric actuating element Bi₁reaches 200 volts, for example, at a time t₂, the transistors Tr₁₁, Tr₁₂are both turned off and then the transistor Tr₁₇ is turned on to shortopposite ends of the piezo-electric actuating element Bi₁ to close theshutter. Consequently, the shutter is closed to terminate the exposureoperation. However, the shutter will not return to its initial positiondue to a hysteresis characteristic of the piezo-electric actuatingelement Bi₁.

Therefore, in order to return the shutter to its initial position, areverse voltage is applied across the piezo-electric actuating elementBi₁ To this end, the transistor Tr₁₈ is turned off and the transistorsTr₁₉, Tr₂₀ are turned on to raise the voltage to the piezoelectricelement B higher than the voltage to the piezo-electric element A.However, if such a voltage is applied suddenly across the piezo-electricactuating element Bi₁, the piezo-electric actuating element Bi₁ will bebent excessively in the reverse direction. Therefore, a resistor Rd isinterposed between the collector of the transistor Tr₂₀ and thepiezo-electric element B of the piezo-electric actuating element Bi₁ Inthis manner, a gradually increasing voltage is applied, across thepiezoelectric actuating element Bi₁ to bend the latter. Then, when theshutter is returned to its initial position (this is detected by turningon of the switch S₅ located at the initial position), the transistorsTr₁₉, Tr₂₀, Tr₁₇ are all turned off to stop application of a highervoltage. This operation is performed for each photographing.

Now, the diagram showing relationships of the aperture value and shutterspeed to the brightness shown in FIG. 11 will be described. Referring toFIG. 11, the program line (a) illustrates a relationship of a shutterspeed priority type, the program line (b) illustrates that of a normaltype, and the program line (c) illustrates that of an aperture prioritytype. In accordance with one of the types selected by operation of themode switches, a combination of an aperture value and a shutter speed asshown in FIG. 11 is obtained with respect to a brightness. For example,if the brightness Bv of an object is Bv=6 and the film sensitivity Sv isSv=5 (ISO=100), then Av=4 (F number=4) and Tv=7 (shutter speed=1/125)are obtained on the program line (a) of the shutter speed priority type,but Av=4.5 (F number=4.8) and Tv =6.5 (shutter speed =1/90) are obtainedon the program line (b) of the normal type, and Av=5 (F number=5.6) andTv=6 (shutter speed=1/60) are obtained on the program line (c) of theaperture priority type. The exposure value Ev determined by the measuredbrightness value Bv and the film sensitivity value Sv which correspondto the limit shutter speed for preventing a camera shake is Ev=7.5 onthe program line (a) of the shutter speed priority type, Ev=8.0 on theprogram line (b) of the normal type, and Ev=9.0 on the program line (c)of the aperture priority type. If the exposure value decreases further,the shutter is closed at this timing while the flash light emission isstarted when the aperture diameter of shutter reaches a suitableaperture value determined by known flashmatic principle in accordancewith a distance to an object. Here, Ev representing the exposure valueis defined by Ev=Bv+Sv=Av+Tv.

Now, the photographing lens actuating circuit 10 shown in FIG. 9 will bedescribed. In the present embodiment, a circular motion of the ratchetof the endless type is converted into a linear motion to actuate thephotographing lens as described hereinabove. Thus, a number of pulsesrequired to move the lens to a position specified by informationregarding a distance from the camera to an object are delivered to thelens actuating circuit 10 by the microcomputer 1 in order to control thedistance of movement of the photographing lens in accordance with thenumber of such pulses. At first, after completion of an exposureoperation, a number of pulses N-Ni which is obtained by substracting anumber N1 of pulses required to move the lens for focusing from a numberN of pulses required to reciprocate the lens from an infinite focusingposition to a nearest focusing position are delivered to the lensactuating circuit 10 by the microcomputer 1 to return the lens to itsinitial position. Such control is achieved by the lens actuating circuitshown in FIG. 9. In the lens actuating circuit 10, a voltage Vacorresponding to an amount of displacement of the feed pawl leverrequired to feed the ratchet by the number of steps required forfocusing the lens is accumulated in a capacitor C₅ while a voltage Vbrequired for returning the lens to its initial position is accumulatedin another capacitor C₄. Then, a transistor Tr₂₄ is turned on to allowthe voltage Va accumulated in the capacitor C₅ to be applied across thepiezo-electric actuating element Bi₂ to displace the piezo-electricactuating element Bi₂ for actuation of the lens for focusing. Then, thetransistor Tr₂₄ is once turned off and another transistor Tr₂₃ is turnedon to allow the voltage Vb accumulated in the capacitor C₄ to be appliedin the opposite direction across the piezo-electric actuating elementBi₂ to return the piezo-electric actuating element Bi₂ to its initialposition. This sequence is repeated for the number N-N1 of pulsesdelivered from the microcomputer 1. In this instance, the transistorTr₂₄ is turned on by turning on of a transistor Tr₂₂ which is turned onwhen an output terminal OP₁₃ of the microcomputer 1 provides an "H"level. Meanwhile, the transistor Tr₂₃ is turned on by turning on of atransistor Tr₂₁ which is turned on when the output terminal OP₁₃provides an "L" level. A delay circuit 35 is connected to an outputterminal OP₁₂ of the microcomputer 1. Just before the microcomputer 1produces a pulse of the "H" level from the output terminal OP₁₃ thereof,the output of the output terminal OP₁₃ presents an "L" level, and aninverted signal of this and a signal of the "H" level from the outputterminal OP₁₂ are applied to an AND circuit AN1 which thus produces asignal of the "H" level to turn the transistors Tr₂₁, Tr₂₃ on to apply areverse voltage across the piezo-electric actuating element Bi₂ therebyto prevent the piezo-electric actuating element Bi₂ from displacing in adirection opposite to a direction in which it should be actuated.Accordingly, a negative voltage will not be applied across thepiezoelectric actuating element Bi₂ before a positive voltage is appliedthereacross. It is to be noted here that the output terminal OP₁₂ of themicrocomputer 1 provides a signal of the "H" level directly before apulse is produced from the output terminal OP₁₃.

Now, the flash circuit 11 shown in FIG. 10 will be described. The flashcircuit 11 shown in FIG. 10 includes a capacitor C₆ for accumulatingenergy for emission of light therein, and a voltage detecting circuitBC₂ for monitoring a charged voltage of the capacitor C₆. The voltagedetecting circuit BC₂ produces a charging completion signal when thevoltage of the capacitor C₆ reaches a desired level. Such a chargingcompletion signal is received by an input terminal IP₉ of themicrocomputer 1 to stop a boosting operation by the boosting circuit 5.The flash circuit 11 further includes a light emission controllingcircuit 36 which operates in response to a light emitting signal fromthe output terminal OP₁₄ of the microcomputer 1 to cause the chargedenergy of the capacitor C₆ to discharge via a xenon tube 37 thereby tocause the xenon tube 37 to emit light.

A sequencing operation of the camera from the circuits described abovewill now be described with reference to a flow chart of themicrocomputer 1 illustrated in FIGS. 12a, 12b and 12c, in whichactuating element is represented as P.E.E. by the abbreviation.

At first, if a lens cover or cap not shown is opened, the switch S₀turns on so that a signal changing from the "H" level to the "L" levelis delivered to an interrupt terminal INT₁ of the microcomputer 1 tointerrupt the microcomputer 1. Consequently, a flow of an interruptroutine "S₀ ON" shown in FIG. 12 is executed. The microcomputer 1resets, at first at step #1 (the word "step" is hereinafter omitted),various flags and output terminals thereof to the "L" level, and then at#2, changes the output terminal OP₀ to the "H" level to turn the powersupply transistor Tr₁ on to supply the power to the various circuits.Then at #3, a signal at the input terminal IP₁ is detected to judgewhether or not the photometry switch S₁ is on. If the switch S₁ is on,then the program advances to #22, but on the contrary if the switch S₁is off, an "S₁ OFF" routine beginning with #4 is executed.

In the "S₁ OFF" routine, at first at #4, the output terminal OP₂ ischanged into the "L" level to once stop a boosting operation of theboosting circuit 5, and then at #5, the output terminal OP₁₀ is changedinto the "L" level to turn the switching circuit 8 off to stop aboosting operation also of the flash circuit 11. After then, at #6, theoutput terminal OP₁₁ is changed into the "H" level to turn the switchingcircuits 6, 7 on in order to charge up the capacitors C₂, C₄, C₅ fordriving the piezo-electric actuating element Bi₁, and then at #7, theoutput terminal OP₂ is changed into the "H" level to turn the transistorTr₂ on to start boosting by the boosting circuit 5.

Then, since a charging completion signal is delivered from the voltagedetecting circuit BC₁ to the input terminal IP₈ if a charged voltage ofthe capacitor C₂ for driving the exposure controlling piezo-electricactuating element Bi₁ reaches a desired level, the microcomputer 1waits, at #8, reception of such a charging completion signal. Uponreception of such a signal, the microcomputer 1 changes, at #9, theoutput terminal OP₁₁ thereof into the "L" level to turn both of theswitching circuits 6, 7 off. In this instance, the charged voltages ofthe capacitors C₄, C₅ are equal to the charged voltage of the capacitorC₂ since their circuit constructions are identical. Subsequently, at#10, the microcomputer 1 changes the output terminal OP₆ into the "L"level to once stop a boosting operation for the capacitor C₃, and thenat #11, changes the output terminal OP₁₀ into the "H" level to turn thetransistor Tr₁₀ of the switching circuit 8 on to start boosting for thecapacitor C₆ of the flash circuit 11. Then, at #12, the output terminalOP₆ is changed into the "H" level again to start boosting for thepiezo-electric actuating element driving capacitor C₃ of the exposurecontrolling circuit 9.

Then, at #13, the microcomputer 1 waits for a charging completion signalto be received from the voltage detecting circuit BC₂ of the flashcircuit 11, and then upon reception of such a charging completion signalat the input terminal IP₉ of the microcomputer 1, it changes, at #14,the output terminal OP₆ into the "L" level to stop the boosting for thepiezo-electric actuating element driving capacitor C₃. Subsequently, at#15, the output terminal OP₁₀ is changed into the "L" level to turn thetransistor Tr₉ off to stop the boosting for the capacitor C₆ of theflash circuit 11, and then at #16, the output terminal OP₀ is changedinto the "L" level to turn the power supply transistor Tr₁ off to stopoperation.

If the photometry switch S₁ is turned on from off or turned off from on,a pulse is produced from the one shot pulse generating circuit 14 and isreceived at another interrupt terminal INT₂ of the microcomputer 1. Uponreception of such an interrupt signal, the microcmputer 1 excecutes aflow of an interrupt routine "S₁ ".

In the interrupt routine "S₁ ", at first at #17, the microcomputer 1judges from an input signal at the input terminal IP₁ thereof whetherthe photometry switch S₁ is on, and if the switch S₁ is off, then theprogram advances to #4 again. To the contrary, if the switch S₁ is on,then the output terminal OP₆ is changed, at #18, into the "L" level tostop the boosting of the piezo-electric actuating element drivingcapacitor C₃, and then at #19 and #20, the output terminals OP₁₀, OP₁₁are both changed into the "L" level to turn all of the switchingcircuits off. Then, at #21, various flags and output terminals arereset, and at #22, the output terminal OP₁₁ is changed into the "H"level to turn the transistors Tr₆, Tr₇ of the piezo-electric actuatingelement switching circuits on to start boosting of the piezo-electricactuating element driving capacitor C₃ whereafter a built-in timer isreset and re-started at #23. The timer is provided for measuring a timenecessary to charge up the capacitors C₂, C₄, C₅ for the piezo-electricactuating elements Bi₁, Bi₂. Thus, a degree of exhaustion of the powersource battery MB may be estimated from the time measured by the timer,and if a time greater than a predetermined time is required for chargingup, warning will be given from the voltage detecting circuit BC₁ as thedegree of exhaustion of the power source battery MB is excessive.

Subsequently, at #24, the output terminal OP₂ of the microcomputer 1 ischanged into the "H" level to start a boosting operation of the boostingcircuit 5, and then at #25 in FIG. 12b, the microcomputer 1 waits acharging completion signal to be received from the voltage detectingcircuit BC₁. Upon reception of such a charging completion signal, thetimer is stopped at #26, and then at #27 and #28, the output terminalsOP₂, OP₁₁ are both changed into the "L" level to stop the boostingoperation by the boosting circuit 5 and to turn the switching circuitoff to stop charging of the piezo-electric actuating element drivingcapacitor C₃.

At #29, the microcomputer 1 judges whether or not a time T required foroperation from #23 to #26 as measured by the built-in timer is equal toor greater than a predetermined time T₁. Then, if the time T thusmeasured is equal to or greater than the predetermined time T₁, it isjudged that the degree of exhaustion of the battery is excessive andhence warning for checking of the battery is given at #30 whereafter theprogram advances to 31. On the contrary, if the measured time T issmaller than the predetermined time T₁, then the program advances to #31while skipping #30.

At #31, the microcomputer 1 delivers a signal indicative of starting ofa distance measuring operation from output terminals thereof to thedistance measuring circuit 13 and delivers, at #32, a signal indicativeof starting of a photometric operation to the photometry circuit 2, andthen waits for a time necessary for the individual measurements.Further, the microcomputer 1 reads, at #34, a film sensitivity Sv fromthe film sensitivity reading circuit 3 and reads, at #35, a brightnessvalue Bv from the photometry circuit 2, and then carries out, at #36, acalculation of Ev=Bv+Sv to find out an exposure value Ev. Subsequently,at #37, the microcomputer 1 reads a measured distance value from thedistance measuring circuit 13, and at #38, a number N1 of pulsesnecessary for actuation of the ratchet is calculated from the measureddistance value.

Subsequently, at #39, the microcomputer 1 determines an exposure modewhich is selected by operation of the mode switches S₆, S₇, and in thecase of the normal mode, a subroutine for the normal mode is executed at#41, but in the case of the aperture priority mode, a subroutine for theaperture priority mode is executed at #42 after execution of #40, orotherwise in the case of the shutter speed priority mode, a subroutinefor the shutter speed priority mode is executed at #43 after executionof #40.

The three subroutines are illustrated in FIGS. 13a, 13b and 13c. Atfirst, in the case of the normal mode, referring to a flow of FIG. 13a,it is judged at step S₁ (the word "step" will be hereinafter omitted)whether the exposure value Ev is equal to or greater than 8.0, and wherethe exposure value Ev is equal to or greater than 8.0, an exposure timeT₃ is determined, at S₂, from the exposure value Ev in accordance withthe program line (b) of FIG. 11. Then at S₃, a time K1 which is longerthan a time required to reach a time T₃ indicated in FIG. 11 is set as atime T₂ at which the xenon tube 37 of the flash circuit 11 is to be lit,and then at S₇, a normal mode flag NMF indicative of the normal mode isset to "1", whereafter the routine of FIG. 12 is re-entered. On thecontrary, where the exposure value Ev is smaller than 8.0 at S1, a flagFLF indicative of a flash photographing mode is set to "1" at S₄, andthen at S₅, an aperture value required for flash photographing isdetermined from the measured distance value in accordance with theprinciple of the flashmatic (here, it is assumed that the amount offlash light to be emitted is constant). Then, a time T₂ corresponding tothe aperture value is determined from the program line (b) of FIG. 11,and then at S₆, the exposure time T₃ then is determined to be 1/30second. Thereafter, the normal mode flag NMF is set to "1" at S₇, andthen the routine of FIG. 12 is re-entered.

Otherwise in the case of the shutter speed preferring mode, referring toFIG. 13b, it is judged at S11 whether or not the exposure value Ev isequal to or greater than 7.5. Where the exposure value Ev is equal to orgreater than 7.5, an exposure time T₃ is determined, at S12, from theexposure value Ev in accordance with the program line (a) of FIG. 11.Then at S13, the time T₂ which defines a timing of emission of flashlight is determined as K₁ in a similar manner as described above, and atS17, a shutter speed priority mode flag SMF indicative of the shutterspeed priority mode is set to "1" whereafter the routine of FIG. 12 isre-entered. To the contrary, where the exposure value Ev is smaller than7.5, the flag FLF indicative of the flash photographing mode is set to"1" at S14. Then at S15, a time T₂ is determined from the program line(a) of FIG. 11 in accordance with the measured distance value, and thenat S16, the exposure time T₃ is determined to be 1/30 second, whereafterthe flag SMF is set at S17 and then the routine of FIG. 12 isre-entered.

Further, in the case of the aperture priority mode, it is judged at S21of FIG. 13c whether or not the exposure value Ev is equal to or greaterthan 9.0. If the exposure value Ev is equal to or greater than 9.0, thenan exposure time T₃ is determined at S22 from the exposure value Ev inaccordance with the program line (c) of FIG. 11. Then at S23, a time T₂at which flash light is to be emitted is determined to be K₁, and thenthe routine of FIG. 12 is re-entered. To the contrary, if the exposurevalue Ev is smaller than 9.0 at S21, the flag FLF indicative of theflash photographing mode is set to "1", and at S25, a time T₂ isdetermined from the program line (c) of FIG. 11 in accoreance with themeasured distance value. Then at S26, the exposure time T₃ is determinedto be 1/30 second, and the routine of FIG. 12 is re-entered. Here, amethod of determining an exposure time T₃ from the calculated exposurevalue Ev and a method of determining a time T₂ at which flash light isto be emitted from the measured distance value may be such that timesT₃, T₂ are read out in accordance with a calculated exposure value and aread measured distance value from respective tables (memories) whichhave been prepared in advance and employ exposure values Ev and measureddistance values as a parameter, respectively.

After the exposure time T₃ and the time T₂ at which flash light is to beemitted have been determined in any subroutine at #41, #42 and #43 shownin FIG. 12b, the microcomputer 1 judges, at #44 shown in FIG. 12c,whether or not the flag FLF indicative of the flash photographing modeis set, and where the flag FLF is in the set state, the program advancesto #45 at which the microcomputer 1 checks a charging completion signalfrom the voltage detecting circuit BC₂ If the charging up of the flashlight emitting capacitor C₆ is not yet completed, the output terminalOP₁₀ is changed at #46 into the "H" level to turn the switching circuit8 on to start boosting of the capacitor C₆. Then at #47, the outputterminal OP₂ is changed into the "H" level to start a boosting operationof the boosting circuit 5, and then at #48, a signal for warning of alow brightness is produced, whereafter the program returns to #45 towait completion of charging up of the capacitor C₆.

Upon completion of charging up of the flash light emitting capacitor C₆,the program advances to #49 and then to #50 at which the outputterminals OP₂, OP₁₀ are changed into the "L" level to stop the boostingoperation of the boosting circuit 5 and turn the switching circuit 8off, respectively. Then at #51, delivery of the signal of warning of alow brightness is stopped, and then the program advances to #52. Alsowhere the flag FLF indicative of the flash photographing mode is not inthe set state at #44, the program advances to #52. Thus at #52, anindication that photographing is possible is given, and then at #53, themicrocomputer 1 waits for the release switch S₂ to be turned on. Then,when the release switch S₂ is turned on, interruptions from theinterrupt terminals INT₁, INT₂ by the switches S₁, S₀ are inhibited at#54 and #55, respectively, whereafter the subroutine of the "LENSACTUATION" at #56 is executed.

The subroutine of the "LENS ACTUATION" is shown in FIG. 14. Referring toFIG. 14, at first at #100, the output terminal OP₁₂ of the microcomputer1 is changed into the "H" level, and then at #101, the number N1 ofpulses are produced from the output terminal OP₁₃. After production ofthe number N1 of pulses, the output terminal OP₁₂ is changed into the"L" level at #102, and then the program returns to #57 of FIG. 12c.

Subsequently at #57 shown in FIG. 12c, the microcomputer 1 advances to asubroutine of "AE". A flow chart of the subroutine is illustrated inFIG. 15. Referring to FIG. 15, at first at #200, the output terminal OP₈is changed into the "H" level so that 0 volts is applied to thepiezo-electric element B of the exposure controlling piezo-electricactuating element Bi₁. Subsequently, an exposure mode is determined at#201 and #202, and in the case of the normal mode, the output terminalOP₅ is changed, at #203, into the "H" level, but in the case of theshutter speed priority mode, the output terminal OP₄ is changed into the"H" level at #204, or otherwise in the case of the aperture prioritymode, the output terminal OP₆ is changed into the "H" level at #205,whereby one of the program lines (a), (b), (c) shown in FIG. 11 isdetermined in accordance with the exposure mode thus selected. Then at#206, the microcomputer 1 waits that the shutter starts to move open andthe switch S₄ is turned on directly before starting of exposure. Then,started when the switch S₄ is turned on, the internal timer is reset andre-started at #207.

Subsequently at #208 and #209, the microcomputer 1 waits for the lapseof the determined flash light emitting time T₂ and the calculatedexposure time T₃. Here, since T₂ elapses earlier than T₃ where T₂ <T₃,the program advances from #208 to #210 at which flash light is emittedat a timing corresponding, to T₂ Then at #211, the microcomputer 1 waitsfor the lapse of the time T₃, and when T₃ elapses, the program advancesto #214 so that a shutter closing controlling sequence may besubsequently executed. To the contrary, where T₂ ≧T₃, T₃ elapses earlierthan T₂. Accordingly, the program advances from #209 to #212 at whichthe microcomputer 1 judges whether or not the flag FLF indicative of theflash photographing mode is set. In case the flag FLF is in the setstate at #212 and hence the camera is in the flash photographing mode,flash light is emitted at #213, and then the shutter closing controllingsequence including #214 is executed. On the contrary, in case the camerais not in the flash photographing mode, the shutter closing controllingsequence is subsequently executed without performing emission of flashlight of #213.

At #214, the output terminals OP₄, OP₅, OP₆ of the microcomputer 1 arechanged into the "L" level to remove application of a voltage across theexposure controlling piezo-electric actuating element Bi₁, and then at#215, the output terminal OP₇ is changed into the "H" level to short thepiezo-electric actuating element Bi₁. Then at #216, the internal timerof the microcomputer 1 is stopped, and then the microcomputer 1 waits,at #217, the shutter to be closed.

Subsequently, at #218, the output terminal OP₈ of the microcomputer 1 ischanged into the "L" level to turn the transistor Tr₁₈ off, and furtherat #219, the output terminal OP₉ is changed into the "H" level to applya positive voltage across the piezo-electric element B relative to theother piezo-electric element A of the piezo-electric actuating elementBi₁. Consequently, a reverse voltage is applied across thepiezo-electric actuating element Bi₁ so that the latter is displaced inthe reverse direction. Consequently, the shutter is actuated further inthe closing direction until its initial position is reached whereuponthe switch S₅ indicating this position is turned on. The microcomputer 1waits, at #220, the switch S₅ to be turned on, and when the switch S₅ isturned on, the output terminals OP₇, OP₉ are changed, at #221, into the"L" level to stop application of the voltage across the piezo-electricactuating element Bi₁, whereafter the program returns to #58 of FIG.12c.

Referring back to FIG. 12c, the microcomputer 1 subtracts, at #58, thenumber N1 of pulses necessary for the actuation described above from thenumber N of pulses necessary for a reciprocating motion of the lens toupdate N1, and then at #59, the program advances again to the subroutineof "LENS ACTUATION" shown in FIG. 14. Then, after completion of thesubroutine of "LENS ACTUATION" of #59, the microcomputer 1 judges at #60whether the photometry switch S₁ is on, and where the photometry switchS₁ is not on, a signal to instruct starting the film to be wound up oneframe distance is delivered, at #61, to the motor controlling circuit 4,and then at #62, the microcomputer 1 waits for the completion of theintended winding up of the film. Then when the switch S which indicatescompletion of the winding up of the film by one frame distance is turnedon, the microcomputer 1 produces, at #63, a signal instructing stoppingof the motor to the motor controlling circuit 4. Then at #64, themicrocomputer 1 enables interruption by the switches S₀, S₁, and theprogram advances to the routine of "S OFF" beginning with #4.

Here, in the embodiment described above, the lens is actuated to thepredetermined in-focus position and returned to the initial positionusing ratchet actuation of the endless type. However, where the modifiedlens actuating mechanism as shown in FIG. 5 is employed instead of thelens actuating mechanism as shown in FIGS. 4a and 4b, naturally thecircuit for controlling the mechanism and the flow chart of operation ofthe microcomputer therein must be modified. In particular, the mechanismshown in FIG. 5 is common to the mechanism shown in FIGS. 4a and 4b inthat the lens is actuated to a predetermined position using ratchetactuation but is designed differently such that when the lens is to bereturned, the stopping lever 33 for preventing reverse rotation may bepressed by the feed pawl lever 31 to remove stopping by the detent lever33 in order to allow the lens to be returned by a force of the spring32. When the stopping by the detent lever 33 is removed, a greateractuating force than a normal actuating force is required. Therefore,the modified circuit is designed to apply a voltage Va+Vb higher than anormal driving voltage Va across the piezo-electric actuating elementBi₂.

A construction of a lens actuating circuit for achieving this is shownin FIG. 16. In the construction shown in FIG. 16, a capacitor C₇ andtransistors Tr₃₀, Tr₃₁, Tr₃₂ are added to the construction of FIG. 9,and also the microcomputer 1 has additional output terminals OP₂₀, OP₂₁.Operation of the lens actuating circuit will be described with referenceto modified or changed portions of flow charts of the microcomputer 1shown in FIGS. 17 and 18. Such modified portions include #56 to #59 ofFIG. 12c and the subroutine of "LENS ACTUATION" shown in FIG. 14. Atfirst, steps #56 to #59 of FIG. 12c are changed as shown in FIG. 17.Referring to FIG. 17, at first at #56', the program advances to thesubroutine of "LENS ACTUATION" in order to actuate the lens to thepredetermined position, and then at #57', the subroutine of "AE" isexecuted to effect exposure controlling. Then at #58', a flag AEEFindicative of completion of exposure is set, and then at #59', theprogram advances again to the subroutine of "LENS ACTUATION" in order toreset the lens. Other operations are identical to those of the flowchart of FIGS. 12a to 12c.

Meanwhile, in the subroutine of "LENS ACTUATION" shown in FIG. 18, themicrocomputer 1 judges at first at #300 whether the flag AEEF is in theset state or not, and where the flag AEEF is not in the set state, theoutput terminal OP₂₀ of the microcomputer 1 is changed, at #301, intothe "H" level to turn the transistors Tr₃₀, Tr₃₁ on, and then at #302,the output terminal OP₁₃ is changed into the "H" level whereafter thenumber N1 of pulses are produced, at #303, from the output terminalOP₁₃. After then, at #304 and #305, the output terminals OP₁₂, OP₂₀ arechanged into the "L" level, respectively, and then the routine of FIG.17 is reentered. On the contrary, where the flag AEEF is in the setstate at #300, the output terminal OP₂₁ is changed, at #306, into the"H" level to turn the transistor Tr₃₂ on so that a voltage of 0 volts isapplied to the fixed end of the piezo-electric actuating element Bi₂.Subsequently, at #307, the output terminal OP₁₃ is changed into the "H"level to apply a voltage of Va+Vb to the other end of the piezo-electricactuating element Bi₂ to increase the amount of displacement of thepiezo-electric actuating element Bi₂. At #308, the microcomputer 1 waitsuntil the piezo-electric actuating element Bi₂ is driven to displaceitself by the intended amount, and at #309, the output terminal OP₁₃ ischanged into the "L" level to stop application of the voltage across thepiezo-electric actuating element Bi₂. Then at #310, the output terminalOP₁₂ is changed into the "H" level to short the piezoelectric actuatingelement Bi₂ to displace the piezoelectric actuating element Bi₂ back toits initial position. Then at #311, the microcomputer 1 waits for a timenecessary for such returning displacement, and then at #312, the outputterminal OP₂₁ is changed into the "L" level to turn the transistor Tr₃₂off. Further at #313, the output terminal OP₂₀ is changed into the "H"level to apply a reverse voltage across the piezo-electric actuatingelement Bi₂ to further drive the piezo-electric actuating element Bi₂ inthe reverse direction in order to reduce the offset or amount ofdisplacement of the piezo-electric actuating element Bi₂ as near to 0 aspossible, whereafter the program returns to the routine of FIG. 17.

Further, in the preceding embodiment, while the photometry switch S₁ ison, boosting for the piezoelectric actuating element driving capacitoris performed and a time required for such boosting is measured in orderto judge a degree of exhaustion of the battery. However, it is alsopossible to perform boosting of the piezo-electric actuating elementdriving capacitor while the release switch S₂ is on.

In such a case, however, it is not desirable to judge a degree ofexhaustion of the battery in response to turning on of the releaseswitch S₂ because the voltage of the battery is not yet stable justafter releasing of the shutter by turning on of the release switch S₂.Accordingly, in order to detect a voltage of the battery, an additionalvoltage detecting circuit may preferably be provided. A block diagram ofa circuit in which such a voltage detecting circuit 38 is additionallyprovided is shown in FIG. 19, and flow charts illustrating a routine ofoperation of the same are illustrated in FIGS. 20a, 20b and 20c. Theflow charts of FIGS. 20a to 20c are modified or changed at two portionscomparing with those of FIGS. 12a to 12c. One of the two portionsinvolves addition after #21 of #21a and #21b wherein at #21a a signalfrom the voltage detecting circuit 38 is received to detect a voltage ofthe battery and then if a drop in voltage is found, warning of suchdropping in voltage is given at #21b. Accordingly, #22 to#24 of FIG. 12aand #25 to #30 of FIG. 12b are omitted here. The remaining one of thetwo modified portions involves addition after #55 as #55a of asubroutine of "P.E.E. BOOSTING" for boosting the piezo-electricactuating element driving capacitor. Details of the subroutine areillustrated in FIG. 21.

In the subroutine of "P.E.E. BOOSTING" of FIG. 21, at first at #400, theoutput terminal OP₁₁ of the microcomputer 1 is changed into the "H"level to turn the switching circuits 6, 7 on to start boosting of thepiezo-electric actuating element driving capacitors C₂, C₄, C₅, and thenat #401, the output terminal OP₂ is changed into the "H" level to starta boosting operation of the boosting circuit 5. Then at #402, themicrocomputer 1 waits for a charging up completion signal to bedelivered from the voltage detecting circuit BC₁ and upon reception ofsuch a charging up completion signal, the microcomputer 1 changes, at#403, the output terminal OP₂ thereof into the "L" level to stop theboosting operation of the boosting circuit 5, whereafter at #404, theoutput terminal OP₁₁ is changed into the "L" level to turn the switchingcircuit 6, 7 off to stop boosting of the piezo-electric actuatingelement driving capacitors C₂, C₄, C₅ After then, the routine of FIG.20c is reentered.

Referring now to FIG. 22, there is shown an exposure controlling circuitwhich is a modification of the circuit shown in FIG. 8. In the modifiedcircuit of FIG. 22, the exposure controlling piezo-electric actuatingelement Bi₁ is used such that it may be offset or displaced from theposition of the displacement "0". Accordingly, a reverse voltage isapplied across the piezo-electric actuating element Bi₁ in order tocompensate for an offset by which the piezo-electric actuating elementBi₁ is not returned to the displacement "0" position (initial position)due to its own hysteresis. Therefore, in the circuit shown in FIG. 22,selected as the initial position is a particular position a littlefarther from a position occupied by an amount of displacement (point (a)indicated in FIG. 7a) which remains when the piezo-electric actuatingelement Bi₁ is shorted after a voltage of 200 volts has been appliedacross the piezo-electric actuating element Bi₁, and the shutter isactuated utilizing displacement of the piezo-electric actuating elementBi₁ from the particular position. To this end, a predetermined fixedvoltage is applied across the piezo-electric actuating element Bi₁ todisplace the latter to the particular position in prior to releasing ofthe shutter, thereby to eliminate an influence of a change in amount ofdisplacement due to the hysteresis by a change in voltage applied. Acircuit diagram of a circuit to realize this is shown in FIG. 22 andflow charts thereof are shown in FIGS. 23a, 23b, 23c, 24 and 25. Now,operation of the circuit shown in FIG. 22 will be described withreference to the flow charts of FIGS. 23a to 25.

Referring to the circuit diagram of FIG. 22 the difference from thecircuit diagram of the exposure controlling circuit shown in FIG. 8 willbe described. At first, in the exposure controlling circuit of FIG. 22,a transistor Tr₄₀ is connected in parallel to the piezo-electricactuating element Bi₁ while the transistors Tr₁₇, Tr₁₈, Tr₁₉ shown inFIG. 8 are omitted. Further, FIG. 22 additionally includes a voltagedetecting circuit BC₃ for detecting a charged voltage of thepiezo-electric actuating element driving capacitor C₃, and a transistorTr₄₁ for controlling power supply to the voltage detecting circuit BC₃The voltage detecting circuit BC₃ delivers a charging up completionsignal to the input terminal IP₁₁ of the microcomputer 1 when chargingup of the capacitor C₃ is completed. Meanwhile, the transistors Tr₄₀,Tr₄₁ are controlled by the output terminals OP₇, OP₈, respectively, ofthe microcomputer 1. Further, the output terminal OP₉ of themicrocomputer 1 for controlling the transistor Tr₁₉ shown in FIG. 8 isomitted.

Comparison between the flow chart of FIGS. 23a to 23c and the flow chartof FIGS. 12a to 12c a difference, in that a subroutine of "P.E.E.RESETTING" for resetting the piezo-electric actuating elements Bi₁, Bi₂is added as #30a after #30 as seen in FIG. 23b. At first, in thesubroutine of "P.E.E. RESETTING" shown in FIG. 24, the microcomputer 1changes, at #500, the output terminal OP₈ thereof into the "H" level toturn the transistor Tr₄₁ on to supply electric power to the voltagedetecting circuit BC₃ in order to cause the voltage detecting circuitBC₃ to detect a voltage. The voltage to be detected is a voltagenecessary to move the piezo-electric actuating element Bi₁ to itsparticular position specified as above. Then at #501, the outputterminal OP₄ is changed into the "H" level to turn the transistors TR₁₁,Tr₁₂ on in order to apply a voltage across the piezo-electric actuatingelement Bi₁ via the transistors TR₁₁, Tr₁₂ to drive the piezo-electricacutating element Bi₁. Then at #502, the microcomputer 1 waits for acharging up completion signal to be received at the input terminal IP₁₁thereof from the voltage detecting circuit BC₃, and upon reception ofsuch a signal, the output terminals OP₄, OP₈ are successively changed,at #503 and #504, into the "L" level to stop application of the voltageacross the piezo-electric actuating element Bi₁ and turn the voltagedetecting circuit BC₃ off, whereafter the routine shown in FIG. 23b isre-entered.

Further, contents of the subroutine of "AE" shown at #57 of FIG. 23cwhich corresponds to #57 of FIG. 12c are modified. The modifiedsubroutine of "AE" is shown in FIG. 25. The subroutine of "AE" shown inFIG. 25 is substantially identical to the subroutine shown in FIG. 15and is different at first in that #200 and #218 to #220 are omittedbecause a reverse voltage is not applied across the piezo-electricactuating element Bi₁ Further, the switch S₅ for detecting returning ofthe piezo-electric actuating element Bi₁ to its initial position inorder to set the piezo-electric actuating element Bi₁ to its initialposition is not necessitated nor such return is monitored. It is to benoted that as such modification is made, a step of operation to changethe output terminal OP₉ of the microcomputer 1 into the "L" level, whichis included in #221 of FIG. 15, is omitted in #221 of FIG. 25.

Here, in the lens actuating mechanism using the ratchet of the endlesstype shown in FIGS. 4a and 4b and in the control of the lens actuatingmechanism, returning of the lens to its initial position is achieved byfeeding the ratchet by driving the piezo-electric actuating element Bi₂by a number of steps which is obtained by subtracting a number N1 ofpulses corresponding to the number of actuated steps necessitated forfocusing from a number N of pulses corresponding to the number of stepsnecessary for the ratchet to cause the lens to make one reciprocation.However, where the modified form shown in FIG. 6 is employed, becausethe switch 34 for detecting that the lens is returned to its initialposition is provided, the piezo-electric actuating element Bi₂ may becontrolled such that when the switch 34 is turned on, driving thereof isstopped to stop movement of the lens.

FIGS. 26 and 27 show flow charts illustrating operation to achieve suchcontrol. FIG. 26 illustrates only modified portions of the flow chartshown in FIGS. 12a to 12c, and only one difference is that, comparingwith the flow charts shown in FIGS. 12a to 12c, #58 is omitted and astep #58a for setting the flag AEEF indicative of completion of exposureis inserted instead. Further, FIG. 27 illustrates modifications of thesubroutine of "LENS ACTUATION" shown in FIG. 18

Referring to FIG. 27, at first at #300, the microcomputer 1 judges,similarly to the flow shown in FIG. 18, whether or not the flag AEEFindicative of completion of exposure is set. Then, in case the flag AEEFis not in the set state, the program advances to #302, then to #303 andthen to #304, but description of operations at these steps is omittedherein because they are identical to those of the preceding embodimentshown in FIG. 18. On the contrary, in case the exposure completion flagAEEF is in the set state at #300, the output terminal OP₁₂ is changed,at #314, into the "H" level, and then at #315, a single pulse isdelivered from the output terminal OP₁₃ to feed the ratchet by one toothspace. Then at #316, the microcomputer 1 judges whether or not theswitch 34 indicative of returning of the lens to its initial position ison, and in case the switch 34 is not on, the program returns to #314 torepeat the sequence of #314 to #316. Thus, when the switch 34 is turnedon, the output terminal OP₁₂ is changed into the "L" level, and then theroutine or FIG. 26 is re-entered. In this instance, the microcomputer 1shown in FIG. 1 necessarily has an input terminal for receiving anon/off signal of the switch 34.

Here, in the exposure controlling circuit and its operation illustratedin FIGS. 22 to 25, a predetermined voltage is applied across thepiezo-electric actuating element Bi₁ in order to fix the initialposition of the latter. However, it is alternatively possible to employa method of fixing the initial position of the piezo-electric actuatingelement Bi₁ wherein at first a predetermined fixed voltage is appliedacross the piezo-electric actuating element Bi₁ to once displace thesame a fixed amount from the position "0" shown in FIG. 7a and then thepiezo-electric actuating element Bi₁ is shorted to return the same to aposition of the hysteresis when the voltage is applied.

Accordingly, the applied voltage is required to be higher than a voltagenecessary to actuate the piezo-electric actuating element Bi₁ to aposition of the hysteresis (point (a) in FIG. 7a) the piezo-electricactuating element Bi₁ has when a highest available voltage is appliedacross the same. It is a matter of course that the voltage variesdepending upon the type of piezo-electric actuating element used and anapplicable highest voltage.

An exposure controlling circuit necessary for putting the method intooperation is identical to that of FIG. 22, and flow charts illustratingoperations of the microcomputer 1 are also same with respect to FIGS. 23and 25. Difference resides only in the subroutine of "P.E.E. RESETTING"of FIG. 24, and such a modified flow chart is shown in FIG. 28.

In the flow chart of FIG. 28, at first at #500, the microcomputer 1changes the output terminal OP₈ thereof into the "H" level to turn thevoltage detecting circuit BC₃ on, and then at #501, changes the outputterminal OP₄ into the "H" level to start charging of the capacitor C₃.Then at #502, the microcomputer 1 waits detection of completion ofcharging up of the capacitor C₃ by the voltage detecting circuit BC₃,and when the charged voltage of the capacitor C₃ reaches a predeterminedlevel, the microcomputer 1 turns the output terminals OP₄, OP₈ thereofoff at #503 and #504, respectively, whereafter it waits, at #505,displacement of the piezo-electric actuating element Bi₁ by apredetermined amount. Then at #506, the microcomputer 1 changes theoutput terminal OP₇ thereof into the "H" level to short thepiezo-electric actuating element Bi₁ and then waits, at #507, for a timesufficient for the piezo-electric actuating element Bi₁ to return to thepredetermined position of the hysteresis. Thereafter, the microcomputer1 changes the output terminal OP₇ thereof into the "L" level, and thenthe routine of FIG. 23b is re-entered. The charged voltage may be such avoltage as described hereinabove. It is to be noted that where anapplicable maximum voltage is applied to the piezo-electric actuatingelement Bi₁, the voltage detecting circuit BC₃ and the transistor Tr₄₁both shown in FIG. 22 may be omitted and #500 and #504 in the flow chartof FIG. 28 may also be omitted. It is further to be noted that in thisinstance the shutter is held from opening by one of the projections 29cof the cam ring 29 provided in the lens actuating mechanism as shown inFIG. 4a.

A further embodiment of the invention is shown in FIGS. 29 to 36. In thecamera of the embodiment, a predetermined position of a shutter blade isdetected in order to control operation of the camera in response to aposition of the shutter blade.

Referring first to FIGS. 29 to 31, a mechanism for actuating a shutterusing a piezo-electric actuating element is shown. The mechanismincludes a pair of shutter blades 51, 52 mounted for pivotal motionaround a common support shaft 53a secured to a shutter front plate 53only a necessary part of which is shown in FIGS. 29 to 31 in order tofacilitate the understanding of construction of the mechanism. As seenin FIG. 29, the shutter blades 51, 52 may have substantially symmetricalshapes and be disposed in substantially symmetrical positions relativeto a line interconnecting the center of an exposure aperture 54a of ashutter base plate 54 and the support shaft 53a except a portion of theshutter blade 51 described below.

As seen in FIGS. 30 and 31, the shutter blades 51, 52 are accommodatedin a spacing formed between the shutter front plate 53 and anintermediate plate 55 which is located between the shutter front plate53 and the shutter base plate 54. The shutter blades 51, 52 haveV-shaped cutaway openings 51a, 52a formed therein, respectively, so thatas the shutter blades 51, 52 are pivoted in a clockwise direction and ina counterclockwise direction, respectively, that is, in an apertureopening direction, around the common shaft 53a, the V-shaped cutawayopenings 51a, 52a will open the exposure aperture 54a of the shutterbase plate 54a.

An opening and closing lever 56 is supported for pivotal motion around afixed shaft 57 mounted on the shutter front plate 53. A pair of engagingpins 56a, 56b are mounted on the opening and closing lever 56 and areengaged with elongated holes 51b, 52b formed in the shutter blades 51,52, respectively, so that as the opening and closing lever 56 is pivotedin a counterclockwise direction around the shaft 57 from a positionshown in FIG. 29 to move the engaging pins 56a, 56b thereon upwardly inFIG. 29, the shutter blades 51, 52 are pivoted in the aperture openingdirection around the shaft 53a. The opening and closing lever 56 furtherhas an elongated hole 56e formed at a portion thereof between theengaging pins 56a, 56b, and the support shaft 53a for the shutter blades51, 52 extends through the elongated hole 56c to allow but limit suchpivotal motion of the opening and closing lever 56 as described above.The engaging pins 56a, 56b on and the elongated hole 56c in the openingand closing lever 56 are located so as to provide symmetrical motions ofthe shutter blades 51, 52 relative to the line passing the center of theexposure aperture 54a and the common support pin 53a. In order toprevent the engaging pins 56a, 56b from interfering with the shutterbase plate 54 upon pivotal motion of the opening and closing lever 56,the shutter base plate 54 has two cutaway portions 54c, 54d formedtherein.

A pair of pins 56c, 56d are mounted at the other end portion of theopening and closing lever 56, and an end of a piezo-electric actuatingelement 58 is received between the pins 56c, 56d. The piezo-electricactuating element 58 is secured at the other end thereof to a holdingplate 60 adjustably secured to the shutter base plate 54.

Accordingly, if a voltage is applied across the piezo-electric actuatingelement 58, the free end thereof will be curved downwardly in FIG. 29 topivot the opening and closing lever in the counterclockwise directionaround the shaft 57 to pivot the shutter blades 51, 52 in the apertureopening direction around the shaft 53a thereby to open the exposureaperture 54a of the shutter base plate 54.

The shutter blade 51 has a greater radius or dimension from the shaft53a than the other shutter blade 52, and a pair of small holes 51A, 51Bare perforated on a same circumferential line of such radial extension51b of the shutter blade 51 around the shaft 53a. An elongated hole 55ais formed at a position of the intermediate plate 55 on the samecircumferential line, and an optical detecting element 59 including alight emitting element and a light receiving element as in aconventional photocoupler is secured adjacent a further cutaway portion54b of the shutter base plate 54 and is positioned such that a beam oflight emitted from the light emitting element thereof may be received bythe light receiving element thereof passing through the elongated hole55a of the intermediate plate 55 and the small hole 51A or 51B when theelongated hole 55a and the small hole 51A or 51B are positioned inregister with each other. Accordingly, when the small hole 51A of theshutter blade 51 is brought into register with the elongated hole 55a ofthe intermediate plate 55 during pivotal motion of the shutter blades51, 52 in the aperture opening direction, an electric pulse is producedfrom the optical detecting element 59, and then when the second smallhole 51B is brought into register with the elongated hole 55a, a secondelectric pulse is produced from the optical detecting element 59. Inparticular, the small hole 51A is positioned on the shutter blade 51 sothat a first electric pulse may be produced when the shutter blades 51,52 are pivoted in the aperture opening direction to a firstpredetermined position just before they begin to provide an opening forexposure, or in other words, so as to detect such a specific position ofthe shutter blades 51, 52. Such a first electric pulse may be used as areference signal from which measurement of exposure time of the cameraas hereinafter described is to be started. Meanwhile, the other smallhole 51B is positioned so as to detect a second predetermined positionsuch as a minimum opening position at which at least photographing isallowed. The latter position signal is also used for control of thecamera as described hereinbelow.

In an aperture closing direction which is opposite to the apertureopening direction, the shutter blades 51, 52 can be pivoted until an endof the shutter blade 51 is engaged with and stopped by a pin 54esecurely mounted on the shutter base plate 54. However, pivotal motionof the shutter blades 51, 52 in the aperture closing direction mayalternatively be limited by the support shaft 53a engaging with an endface of the elongated hole 56c of the opening and closing lever 56.

In operation, a negative or reverse voltage may first be applied to thepiezo-electric actuating element 58 to pivot the shutter blades 51, 52in the aperture closing direction to the hole or limit position definedby the pin 54e. Subsequently, a positive voltage is applied across thepiezo-electric actuating element 58 to pivot the shutter blades 51, 52in the aperture opening direction until a selected opening of theshutter aperture is reached. During such pivotal motion of the shutterblades 51, 52 in the aperture opening direction, the optical detectingelement 59 first detects the first small hole 51A of the shutter blade51 to develop an electric pulse signal indicating arrival of the shutterblades 51, 52 at the first predetermined position just before they beginto provide an opening for exposure and then detects the second smallhole 51B to develop a second electric pulse signal indicating arrival atthe second predetermined position. After then, a negative voltage isapplied again across the piezo-electric actuating element 58 to pivotthe shutter blades 51, 52 to their respective initial positions.

Now, construction of an electric circuit of the camera will be describedwith reference to FIG. 32. The circuit shown includes a microcomputer 61which controls sequencing of the camera and calculates an exposure ofthe camera. The circuit further includes a photometry circuit 62 formeasuring a brightness of an object of photographing via a lens (notshown) incorporated in the camera independently of a photographing lensand for producing a digital signal of the measured brightness value Bvrepresented in A.P.E.X. system to the microcomputer 61. A filmsensitivity reading circuit 63 reads a sensitivity Sv of a filmrepresented in A.P.E.X. system and produces a digital signal of the filmsensitivity Sv thus read to the microcomputer 61. A position detector 64corresponding to the optical detecting element 59 described abovedetects a degree of opening of the shutter and produces an electricpulse. A distance measuring circuit 65 measures a distance to an objectand produces a digital signal indicative of the measured distance to themicrocomputer 61. A flash circuit 66 is of a known type and includestherein a boosting circuit for boosting a voltage of a battery E whichserves as a power source to a level required to drive the piezo-electricactuating element 58 to actuate the shutter described above and to drivea flash device to emit flash light. The flash circuit 66 thus receives asignal from the microcomputer 61 and causes the flash device to emitflash light. The circuit of FIG. 32 further includes a driving circuit67 for driving the piezo-electric actuating element 58, which will behereinafter described. A lens driving circuit 68 is also provided andoperates in response to information of a measured distance to drive alens to move to a specified position.

The circuit further includes a reverse charging preventing diode D₅₁, abackup capacitor C for the microcomputer 61, and a power supplytransistor Tr₅₁ which becomes conductive to supply power of a voltageV₅₁ to the photometry circuit 62, the film sensitivity reading circuit63, the position detector 64, the distance measuring circuit 65, thepiezo-electric actuating element driving circuit 67 and the lens drivingcircuit 68. Meanwhile, the flash circuit 66 is supplied with power of avoltage V₅₀ directly from the power source E, and the piezo-electricactuating element driving circuit 67 is additionally supplied with powerof 200 volts from the flash circuit 66.

A main switch S₅₀ is connected to the microcomputer 61 and is turned onand off if, for example, a lens cover not shown is opened and closed,respectively. As the main switch S₅₀ is turned on, an interrupt routineas illustrated in flow charts of FIGS. 33a, 33b and 33c is executed. Aphotographing preparing switch S₅₁ is turned on when a release buttonnot shown is depressed to a first stroke or depth, and as the switch S₅₁is turned on, the camera makes preparations for subsequentphotographing, including photometry and measurement of a distance to anobject. A release switch S₅₂ is turned on when the release button isdepressed to a second stroke greater than the first stroke, and as therelease switch S₅₂ is turned on, a photographing operation is carriedout.

Referring now to FIG. 34, detailed construction of the piezo-electricactuating element driving circuit 67 is shown. The driving circuit 67includes transistors Tr₅₂ to Tr₅₄, a Zener diode ZD, diodes D₅₁ to D₅₃,a piezo-electric actuating element Bi corresponding to thepiezo-electric actuating element 58 of FIG. 29, resistors R₅₁ to R₅₅,and a variable resistor VR₅₁ which cooperates with a constant-currentregulated power source I and is adjusted to cause the transistor Tr₅₂ toprovide a predetermined constant-current flow Il therefrom. An auxiliarycapacitor C_(A) is connected so that a reverse voltage equal to orhigher than 50 volts may be applied across the piezo-electric actuatingelement Bi even if the voltage of a main capacitor C_(M) included in theflash circuit 66 becomes lower than a predetermined voltage of 50 voltsas a result of lighting of the flash device. A reverse chargingpreventing diode D₅₅ is connected to prevent a charge of the capacitorC_(A) from flowing to the flash device.

Operation of the piezo-electric actuating element driving circuit 67will now be described. At first, operation of the circuit 67 when thepiezo-electric actuating element Bi is to be driven to open the shutterwill be described. When no signal is received from the microcomputer 61,a voltage across the piezo-electric actuating element Bi, that is,between points 69 and 70 of the circuit 67 in FIG. 34, is equal to avoltage supplied from the flash circuit 66. In this state, if a signalof a high (H) level instructing opening of the shutter is received froma terminal OP₃ of the microcomputer 61, the transistor Tr₅₂ is turnedon. As a result, a capacitor component of the piezo-electric actuatingelement Bi is charged with a constant-current flow I₁ so that thevoltage across the piezo-electric actuating element Bi increasesgradually to open the shutter. Here, resistances of the resistors R₅₂,R₅₃ should be selected, based on a voltage across the piezo-electricactuating element Bi produced by the resistor R₅₁ and theconstant-current flow I₁, so that the transistor Tr₅₄ may not be turnedon by the voltage. In this instance, the voltage at the point 69 islower than the voltage at the point 70. Therefore, in order to preventelectric current from flowing through the Zener diode ZD, the diode d₅₂is connected in a direction shown in FIG. 34 in series to the Zenerdiode ZD.

Now, operation of the piezo-electric actuating element driving circuit67 when a reverse voltage is to be applied to the piezo-electricactuating element Bi will be described. Such a reverse voltage isapplied twice to the piezo-electric actuating element Bi: it is appliedfor the first time when the photographing preparing switch S₅₁ is turnedon, and for the second time when the shutter is to be closed. In eithercase, signals of an H level are delivered from terminals OP₃, OP₄,respecively, of the microcomputer 61 to turn on the transistors Tr₅₂,Tr₅₃, respectively. As the transistor Tr₅₃ is turned on, the transistorTr₅₄ is turned on. Consequently, the voltage at the point 69 becomeshigher than the voltage at the point 70. In this instance, a voltagebetween the points 69 and 70, that is, a voltage across thepiezo-electric actuating element Bi, is determined by the Zener diodeZD, and here in the embodiment, the voltage is selected to be 50 volts.It will be appreciated that, in this instance, the signal from theterminal OP₃ of the microcomputer 61 may otherwise be at a low (L)level. It is to be noted that the diode D₅₃ is provided to prevent anegative voltage of a high magnitude from appearing at the point 69directly after the transistor Tr₅₃ has been turned on and that theresistor R₅₅ is provided to prevent a voltage from being applied to thepiezo-electric actuating element Bi when leak current may flow from thepoint 69 to the ground in order to prevent the shutter from being openedwhen the camera is inoperative.

On the other hand, the flash circuit 66 may be regarded as a compositecircuit of the boosting circuit 5 and, for example, the exposurecontrolling circuit 9 of the first embodiment shown in FIG. 8 and mayinclude a DC-DC converter, a capacitor for accumulating therein electriccurrent from the converter, a detecting circuit for detecting a voltageacross the capacitor, a trigger circuit for causing the capacitor todischarge an accumulated charge, and a xenon tube. In the flash circuit66 of such a construction, the detecting circuit may be constituted todetect voltages of 250, 100 and 200 volts and deliver, when suchvoltages are detected, charging completion signals CC1, CC2 and CC3 ofan H level from respective terminals thereof. In this instance, fordetection of the voltage of 100 volts, only a voltage higher than 50volts is necessary because the voltage of 50 volts is used as a reversevoltage to the piezo-electric actuating element Bi as describedhereinabove in connection with the piezo-electric actuating elementdriving circuit 66. On the other hand, the voltage of 200 volts is avoltage necessary for the piezo-electric actuating element Bi to bedriven sufficiently until the shutter is opened to reach an allowablemaximum exposure aperture and also for the flash device to be driven toemit flash light.

Subsequently, operation of the camera described above will be describedwith reference to FIGS. 33a to 33c.

If the main switch S₅₀ shown in FIG. 32 is turned on, a signal changingfrom an H level to an L level is received by a terminal S₀ INT of themicrocomputer 61. Upon reception of the signal, the microcomputer 61executes a program which is illustrated in flow charts of FIGS. 33a to33c.

Referring first to FIG. 33a, the microcomputer 61 at first resets flagsand ports thereof at step #601, and then at #602, it delivers from aterminal OP₂ thereof a boosting starting signal STA of the H level tocause the flash circuit 66 to start boosting. Upon reception of thesignal STA, the flash circuit 66 thus starts its boosting operation.Then at #603, the microcomputer 61 checks a level at a terminal IP₂thereof to determine whether or not the photographing preparing switchS₅₁ is on, and if the level is "H", then the microcomputer 61 determinesthat the photographing preparing switch S₅₁ is off and advances theprogram to #604 at which it determines whether or not a flag CCFindicating whether or not the voltage across the capacitor C_(M) of theflash circuit 66 is equal to or higher than 250 volts, in other words,whether or not the capacitor C_(M) has been charged up to 250 volts, isin a set state. If the flag CCF is in the set state, then themicrocomputer 61 checks, at #605, a level at a terminal IP₁ thereof todetermine whether the main switch S₅₀ is off. In case the terminal IP₁is at the "H" level, the microcomputer 1 determines that the main switchS₅₀ is off and thus stops its operation (#606). On the contrary, if theterminal IP₁ is at the "L" level at #605, the microcomputer 1 determinesthat the main switch S₅₀ is on and thus returns the program to #603 atwhich it waits until the photographing preparing switch S₅₁ is operated.

Meanwhile, in case the flag CCF indicating completion of charging up ofthe capacitor C_(M) of the flash circuit 66 is not in the set state at#604, the program advances to #607 at which a level of the signal CC1from the flash circuit 66 is checked to determine the charged voltage ofthe capacitor C_(M) is equal to or higher than 250 volts. Here, if thesignal CC1 is at the "L" level, the microcomputer 61 determines that thevoltage of 250 volts is not yet reached and thus starts boosting at #610whereafter the program returns to #603. On the contrary, if the signalCC1 is at the "H" level at #607, the microcomputer 61 determines thatthe voltage of 250 volts is reached and thus stops boosting at #608 andthen sets a flag CCF indicating completion of the charging up of thecapacitor C_(M) to "1" at #609. After then, the program returns to #603.Accordingly, when the main switch S₅₀ is on and the photographingpreparing switch S₅₁ is not on or when the release button is brought outof a depressed condition, boosting is carried out only once.

On the other hand, in case the photographing preparing switch S₅₁ is onat #603, the program advances to #611 at which a level of the signal CC2from the flash circuit 66 is checked to determine whether the chargedvoltage is equal to or higher than 100 volts. In case the signal CC2 isat the "L" level, the microcomputer 61 determines that the voltage of100 volts is not yet reached and thus delivers, at #612, a signal STA ofthe "H" level in order to start or continue boosting. After then, theprogram returns to #611 in order to wait the capacitor C_(M) to becharged to the voltage of 100 volts. Thus, in case it is detected at#611 that the voltage of 100 volts is reached, the signal STA ischanged, at #613, into the "L" level to stop boosting. Subsequently at#614, the microcomputer 61 changes a terminal OP₁ thereof into the "H"level to turn the power supply transistor Tr₅₁ on to start the powersupply to the several circuits connected to the same. Thereupon, thephotometry circuit 62 and the distance measuring circuit 65 start theiroperation. Then at #615, the microcomputer 61 resets and startsoperation of an internal timer T₁ thereof. The timer T₁ provides avoltage application time during which a reverse voltage is to be appliedto the piezo-electric actuating element Bi (58 in FIG. 29) for actuatingthe shutter blades 51, 52 in order to set the same to its home positionto attain a following end.

Referring to FIG. 35, there are shown characteristics of opening of ashutter which also acts as an aperture design relative to a time ofapplication of a voltage to the piezo-electric actuating element Bi. InFIG. 35, the axis of abscissa indicates a time of voltage application,and the axis of ordinate indicates opening (angular displacement) of theshutter blades. In the present embodiment, the piezo-electric actuatingelement Bi is charged with a constant-current flow. Accordingly, thevoltage of the piezo-electric actuating element Bi increases inproportion to the time of voltage application. Therefore, the axis ofabscissa may indicate the voltage of the piezo-electric actuatingelement Bi. In FIG. 35, a curve ○a indicates opening of the shutter whenthe piezo-electric actuating element Bi for actuating the shutter isactuated or started from a specific or predetermined home positiondenoted at SPa which corresponds to a position of the piezo-electricactuating element 58 where the shutter blade 51 is stopped by the pin54e, and a curve b indicates an opening characteristic of the shutterwhen the piezo-electric actuating element Bi is actuated or started froma position denoted at SPb which is displaced from the home position SPa.During a period of time T₁ of about 20 msec. from starting ofapplication of the voltage to Bi, while the piezo-electric actuatingelement Bi urges the shutter blades, a force of statical friction of theshutter blades prevails over an urging force of the piezo-electricactuating element Bi, and hence the shutter remains at its initialposition. After the time T₁ has elapsed, the piezo-electric actuatingelement Bi starts its deformation and operation to actuate the shutterblades. Thus, as time passes and hence the charged voltage of thepiezo-electric actuating element Bi increases, the shutter blades aredisplaced progressively. In this instance, the amount of displacement ofthe shutter blades is irrespective of at which position thepiezo-electric actuating element Bi is positioned and is a function of atime of voltage application to the piezo-electric actuating element Biwhere the voltage applied is constant. Accordingly, the shapes of thetwo curves ○a , ○b are similar to each other as seen in FIG. 35.

Now, examination is made here of a case wherein the exposure valuecorresponds to a minimum aperture diameter. In FIG. 35, the period oftime required to move the shutter blades from a first predeterminedposition at which the small hole 51A of the shutter blade 51 is detectedby the optical detecting element 59 to start measurement of the exposuretime to a second predetermined position at which the shutter bladesprovide a minimum opening at which at least photographing is allowed isrepresented by Ta where the shutter blades are actuated from the homeposition and by Tb where the shutter blades are actuated from a positiondisplaced from the home position. Because opening of the shutterprogressively increases as the time of voltage application to thepiezo-electric actuating element Bi passes, the time Tb is greater thanthe time Ta, that is Tb>Ta. Accordingly, the shutter speed (or openingtime) varies depending upon from which position the piezo-electricactuating element Bi and hence the shutter blades are actuated, and suchvariation of the shutter speed will result in an error in exposure. Inthe present embodiment, since the exposure is controlled by the openingtime of the shutter, the diameter of the aperture varies depending uponan initial position of the piezo-electric actuating element, which willalso result in an error in exposure. It is to be noted, however, thatthe opening time of the shutter will vary where an exposure value isselected which corresponds to an aperture of the minimum opening.

In this manner, actuation of the piezo-electric actuating element Bifrom a position displaced from its home position will apparently resultin an error in exposure. Therefore, in order to prevent this, a reversevoltage is applied to the piezo-electric actuating element Bi to onceset the same to its home position.

Referring back to FIG. 33a, after starting of operation of the timer T₁for reverse voltage application to 0 the piezo-electric actuatingelement Bi at #615, the microcomputer 61 changes, at #616, the terminalsOP₃, OP₄ thereof into the "H" level to cause the driving circuit 67 toapply a voltage of -50 volts across the piezo-electric actuating elementBi (a voltage at the point 70 is lower than a voltage at the point 69,FIG. 34). Such application of the negative voltage continues for aperiod of time of 50 msec. (#617), and during the period of time, theshutter blades 51, 52 are pivoted in the aperture closing directionuntil the shutter blade 51 is engaged with and stopped by the pin 54e.The shutter blades 51, 52 maintain the stopped positions until they aresubsequently pivoted in the aperture opening direction.

Referring now to FIG. 33b, after the time of 50 msec. has passed at thetimer T₁, the microcomputer 61 changes, at #618, the terminals OP₃, OP₄thereof into the "L" level to stop the application of the reversevoltage of 50 volts. Subsequently at #619, the microcomputer 61 waitsuntil a time of 100 msec. elapses at the timer T₁ (as measured from step#615). This time of 100 msec. is selected in order to assure that aphotometric operation and a distance measuring operation are completedby the photometry circuit 62 and the distance measuring circuit 65,respectively. After lapse of the time of 100 msec., the microcomputer 61reads, successively at steps #620, #621 and #622, a brightness value Bv,a measured distance value and a film sensitivity Sv from the photometrycircuit 62, the distance measuring circuit 65 and the film sensitivityreading circuit 63, respectively, and then calculates, at #623, anexposure value Ev using an equation Ev=Bv+Sv. Then at #624, the exposurevalue Ev is discriminated whether it is equal to or greater than "9",and if it is smaller than "9", then a flag LLF indicating a lowbrightness is reset to "0" at #625, but on the contrary if the exposurevalue Ev is greater than "9", the flag LLF is reset to "0"at #626.Subsequently at #627, the microcomputer 61 checks a level at a terminalIP₆ thereof, that is, a signal CC3, to detect whether the capacitorC_(M) of the flash circuit 66 is charged to a voltage of 200 voltsrequired to actuate the piezo-electric actuating element Bi by apredetermined amount. If the terminal IP₆ is at the "H" level whichindicates the capacitor C_(M) is charged up to 200 volts, themicrocomputer 61 determines that the camera is ready for releasing ofthe shutter, that is, the shutter will open regularly, and then checks,at #632, a level at a terminal IP₃ thereof to determine whether or notthe release switch S₅₂ is on. Here, if the release switch S₅₂ is on,that is, if the terminal IP₃ is at the "L" level, then the microcomputer61 executes a sequence of release controlling steps beginning with #636shown in FIG. 33c. To the contrary, if the release switch S₅₂ is not onat #632 and hence the terminal IP₃ is at the "H" level, then themicrocomputer 61 detects at #633 whether or not the photographingpreparing switch S₅₁ is on. In case the switch S₅₁ is on and hence theterminal IP₂ of the microcomputer 61 is at the "L" level, the programreturns to #627, but on the contrary in case the switch S₅₁ is off andhence the terminal IP₂ is at the "H" level, the microcomputer 61determines that the photographer has taken a hand off the release buttonto stop a photographing operation and thus changes, at #634, theterminal OP₁ into the "L" level to turn the power supply transistor Tr₅₁off. Subsequently at #635, the microcomputer 61 resets the flag CCFindicating completion of charging of the capacitor C_(M), and thenreturns the program to #603 in order to effect charging of the capacitorC_(M) once again. On the other hand, if it is determined at #627 fromthe signal CC3 that the capacitor C_(M) is not yet charged up to avoltage equal to or higher than 200 volts, the signal STA is changed, at#628, into the "H" level to start boosting, and then at #629, a state ofthe photographing preparing switch S₅₁ is checked to determine whetheror not it has been turned off. In case the switch S₅₁ is off and hencethe terminal IP₂ is at the "H" level, the microcomputer 61 determineseither that no releasing operation is performed while the release buttonhas been depressed to its second stroke or that the photographer hastaken a hand off the release button in order to only stop aphotographing operation, and thus advances the program to #634. On thecontrary, if the photographing preparing switch S₅₁ is on and hence theterminal IP₂ is at the "L" level at #629, the signal CC3 is checked, at#630, to determine whether or not the charged voltage reaches 250 volts.Here, if the capacitor C_(M) is charged up to a voltage equal to orhigher than 250 volts and hence the terminal IP₆ is at the "H" level,then the signal STA is changed, at #631, into the "L" level to stopboosting whereafter the program returns to #629. On the other hand, ifthe capacitor C_(M) is not yet charged up to 250 volts at #630 and hencethe terminal IP₆ is at the "L" level, the program returns to #629skipping #631. By such a sequence of operations as described above, therelease of shutter is interrupted once when the charged voltage of thecapacitor C_(M) does not reach a voltage of 200 volts at which regularoperation of the shutter is assured.

Referring now to FIG. 33c, at #636 to which the program advances from#632 of FIG. 33b when the release switch S₅₂ is on and hence theterminal IP₃ is at the "L" level, the microcomputer 61 delivers a lensshifting amount signal to the lens driving circuit 68. This signalincludes information of a shifting amount of lens required for shiftingthe lens to its in-focus position and serves also as a lens shiftingstart signal. Thus, upon reception of the signal, the lens drivingcircuit 68 drives or shifts the lens by such a specified amount ordistance, and then when such shifting of the lens is completed, itdevelops a stopping signal STP of an "H" level. Upon reception of thestopping signal STP at #637, the microcomputer 61 resets and startsoperation of the timer T₁ at #638. Here, the timer T₁ serves as alimiting timer used for prevention of an operation in error and providesa predetermined period of time within which a signal indicating thefirst or second predetermined position of the shutter blades is to becoupled to the microcomputer 61 in order that when such a signal is notreceived from the position detector 64 (optical detecting element 59 inFIG. 29) within the predetermined period of time of the timer T₁ by somereasons, for example, due to breaking of wire or trouble of aphotocoupler of the optical detecting element, the shutter blades may beclosed after lapse of the predetermined period of time.

Subsequently, at #639, the microcomputer 61 discriminates whether or notthe flag LLF indicating a low brightness condition is in the set state,and if the flag LLF is in the set state, the microcomputer 61calculates, at #640, an exposure time (T₂) corresponding to an aperturevalue providing appropriate exposure for flash photographing from thedistance information received at #621 from the distance measuringcircuit 65. On the contrary, if the flag LLF is not in the set state at#639, the microcomputer 61 calculates, at #641, from the exposure valueEv calculated at #623, an exposure time (T₂) corresponding to anaperture value providing appropriate exposure for photographing.

After completion of calculation of an exposure time at #640 or #641, themicrocomputer 61 changes the terminal OP₃ thereof into the "H" level tostart exposure, that is, movement of the shutter blades. Then, themicrocomputer 61 waits for a time of 300 msec. at #644 until a firstposition signal PC₁ indicating the first predetermined position of theshutter blades just before exposure is started, that is, a rising edgeof a pulse, is received, at #643, at a terminal IP₈ of the microcomputer61 from the position detector 64. In case no first position signal PC₁is received within the time of 300 msec., the program advances to #651.On the other hand, in case the first position signal PC₁ is receivedwithin the time of 300 msec., the microcomputer 61 resets and startsoperation of the exposure timer T₂ at #645. Subsequently, themicrocomputer 61 waits, at #647, for a time of 300 msec. as measuredfrom starting of operation of the timer T₁ at #638 until a secondposition signal PC₂ indicating the minimum opening position of theshutter blades at which at least photographing is allowed is receivedfrom the position detector 64 at #646. In case the second positionsignal PC₂ is received from the position detector 64, the microcomputer61 waits until the exposure time calculated at #640 or #641 elapses atthe timer T₂ During the exposure time, the shutter blades are pivoted inthe aperture opening direction until the diameter of aperture diaphragmreaches a suitable value. After lapse of the exposure time, themicrocomputer 61 checks, at #649, the flag LLF indicating a lowbrightness state. Here, if the flag LLF is in the set state, themicrocomputer 61 delivers from a terminal OP₅ thereof a pulse signal Triinstructing lighting of the flash, and then the program advances to asequence of shutter closing operations beginning with #651. Also wherethe flag LLF is not in the set state at #649, the program advances to#651 of the shutter closing sequence skipping #650.

Here, description is given of a reason why a signal instructing closingof the shutter is not started until the second position signal PC₂, thatis, a minimum shutter opening signal, is received even if the exposuretime (T₂) has elapsed. In the present embodiment, a piezo-electricactuating element also known as a bimorph is employed as a drivingsource of the shutter, and if its initial position is not fixed orstabilized as described hereinbefore, the opening speed of the shutterblades will not be stabilized and sometimes the shutter may not beopened at all during the exposure time (T₂) In order to prevent this, ashutter closing instruction is not started until a minimum shutteropening signal is received. It will be appreciated that the unstablenessin opening speed of the shutter may be caused, in addition to the reasondescribed hereinabove, by a fluctuation of the characteristic of thepiezo-electric actuating element (relationship between a voltage and anopening characteristic), by a fluctuation of a driving force required toopen the shutter due to a temperature, and by a fluctuation of such adriving force due to a difference in posture. It is to be noted that ashutter having such an unstable opening speed requires similar control.

Referring back to FIG. 33c, as described above, in case the secondposition signal PC₂, that is, a signal indicating a minimum shutteropening, is not received from the position detector 64 within the timeof 300 msec., the microcomputer 61 determines that no second positionsignal PC₂ is produced from the position detector 64 by some reasons andthus advances the program to #651 in order to effect a shutter closingoperation. At #651, the microcomputer 61 resets and starts operation ofthe timer T₁, and then at #652, it changes a terminal OP₄ into the "H"level to apply a reverse voltage of 50 volts to the piezo-electricactuating element Bi to close the shutter. Then at #653, themicrocomputer 61 waits that the time of 50 msec. elapses at the timerT₁, and after lapse of 50 msec., the microcomputer 61 changes, at #654,the terminals OP₃, OP₄ into the "L" level to stop application of thereverse voltage of 50 volts to the piezo-electric actuating element Bi.After then, at #655, the microcomputer 1 waits until the photographingpreparing switch S₅₁ is turned off to change the terminal IP₂ into the"H" level, and then when the switch S₅₁ is turned off, the chargingcompletion flag CCF is reset to zero at #656, whereafter the programreturns to #603 in order to charge up the capacitor C_(M) of the flashcircuit 66 after completion of the preceding photographing to preparefor subsequent photographing.

It is to be noted that while in the embodiment described above thecapacitor C_(M) of the flash circuit 66 is charged to a predeterminedvoltage (100 volts) if the predetermined voltage is not yet reached justafter the photographing preparing switch S₅₁ has been turned on, it mayotherwise be charged during a predetermined time period each time theswitch S₅₁ is turned on at #603. A flow chart of a program in which suchmodification is incorporated is shown in FIG. 36. The flow chart of FIG.36 generally corresponds to the flow chart of FIG. 33a, and steps #611and #612 in FIG. 33a are replaced by steps #661, #662 and #663 in FIG.36. In particular, the microcomputer 61 resets and starts operation ofthe timer T₁ at #661, and then at steps #662 and #663, it causes theflash circuit 66 to start and continue boosting for a predeterminedperiod of time (50 msec.) until the boosting is stopped subsequently at#613.

An alternative modification is also possible wherein no boostingoperation is effected just after the photographing preparing switch S₅₁has been turned on. In this modification, the steps #611 and #613 ofFIG. 33a should be omitted. In this instance, even if a reverse voltageis applied to the piezo-electric actuating element Bi when the capacitorC_(M) for the piezo-electric actuating elelemt Bi is not yet charged toa voltage of 50 volts, the piezo-electric actuating element Bi may notbe set to its home position. In such a case, however, it is determinedat #627 that the capacitor C_(M) is not yet charged sufficiently, andhence the release of the shutter is interrupted to prevent a releasingoperation. Accordingly, an operation in error (error in exposure) can beprevented.

It is to be noted that while in the present embodiment a brightnessvalue is stored once into a memory and such a stored brightness value isrecalled later in order to determine an exposure value, such abrightness value may otherwise be read on a real time basis from thephotometry circuit 62. In this case, the photometry circuit 62 willbegin its light measuring operation when the second position signal PC₂is received from the position detector 64.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to be notedhere that various changes and modifications will be apparent to thoseskilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention, theyshould be construed as being included therein.

What is claimed is:
 1. A camera, comprising:a power source; boostingmeans for boosting a voltage of said power source; charging means foraccumulating therein energy boosted by said boosting means;piezo-electric means; driven means including a shutter connected to beactuated by said piezo-electric means; driving and controlling means fordriving and controlling said piezo-electric means by energy accumulatedin said charging means; and shutter opening speed controlling meanshaving means for controlling a rate of current flow to be supplied tosaid piezo-electric means per unit time to control the actuating speedof said piezo-electric means and hence the opening speed of saidshutter.
 2. A camera, comprising:a power source; boosting means forboosting a voltage of said power source; charging means for accumulatingtherein energy boosted by said boosting means; piezo-electric means;driven means including a shutter connected to be actuated by saidpiezo-electric means; driving and controlling means for driving ancontrolling said piezo-electric means by energy accumulated in saidcharging means; a capacitor parallely connected directly to saidpiezo-electric means to stabilize the speed of displacement of saidpiezo-electric means; and exposure amount controlling means forcontrolling said driving and controlling means to open said shutter andto close said shutter when an appropriate exposure amount is obtained.3. A camera, comprising:a power source; boosting means for boosting avoltage of said power source; charging means for accumulating thereinenergy boosted by said boosting means; piezo-electric means; drivenmeans including a shutter connected to be actuated by saidpiezo-electric means; means for selecting a photographing mode out of aplurality of photographing modes; driving and controlling meansincluding shutter speed controlling means for controlling a currentwhich flows to said piezo-electric means in accordance with a selectphotographing mode; and exposure amount controlling means forcontrolling said driving and controlling means to close said shutterwhen an appropriate exposure amount is obtained.
 4. A camera accordingto claim 3, wherein said photographing mode selecting means is manuallyoperable and selects one of a shutter speed priority automatic exposuremode, an aperture value priority automatic exposure mide and a manualmode.